This invention relates to writing data on an optical storage medium.
When data is written to a recordable optical device, one common recording scheme requires that the data be continuously written at the recording rate of the optical device without interruption until the recording medium in the device is completely recorded. During writing, the data is transferred from, e.g., a main memory of a host computer, a hard drive, a tape, or another optical disk; to a temporary memory location (referred to as the write buffer) on the drive of the optical device and is pulled out of the write buffer in a first-in-first-out (FIFO) basis as needed for writing on the disk. If the write buffer is empty when the recorder requests data at any point during the recording process, the recording process aborts and the CD-R is typically ruined. The emptying of the write buffer while the recorder still needs data is referred to as buffer underrun.
As CD-R recording rates increase to 2xc3x97, 10xc3x97 and even 40xc3x97, even small interruptions in data transfer to the write buffer can produce buffer underrun. To reduce the chance of buffer underrun, conventional recordable optical devices include a write buffer with a large data storage capacity. Thus, there is a tradeoff between increasing the recording rate and avoiding the high cost associated with larger write buffer memories.
In one embodiment, the invention is a method for writing data on an optical storage medium in an optical storage device. The method includes transferring data by a direct memory access process from a host buffer allocated in a memory of a host device to a local write buffer associated with the optical storage device. The data is then written from the write buffer to the optical storage medium.
In another embodiment, the invention is an electronic device that includes a memory, a direct memory access controller, a data storage medium in an optical storage. device, and a driver for the optical storage device. The driver is programmed to execute instructions to write the medium, including transfer of data to a host buffer allocated in the memory of the device, and activation of the direct memory access controller to transfer data by a direct memory access process from the host buffer to a local write buffer associated with the optical storage device.
In a third embodiment, the invention is an article comprising a computer-readable medium that stores computer-executable instructions for writing an optical medium in an optical device. The instructions cause a computer to transfer data to a host buffer allocated in the memory of the device and activate the direct memory access controller to transfer data by a direct memory access process from the host buffer to a local write buffer associated with the optical storage device. Data in the host buffer are available to the write buffer such that the write buffer is not underrun while the data storage medium is completely written without interruption.
In a fourth embodiment, the invention is a recordable optical device having a write buffer with a data storage capacity of less than about 256 kB, preferably about 32 kB.
A fifth embodiment of the invention is an optical data storage system including an optical device having a data storage medium, and an article comprising a computer-readable medium that stores computer-executable instructions for writing the optical medium. The instructions cause a computer to transfer data to a host buffer allocated in the memory of the device; and activate the direct memory access controller to transfer data by a direct memory access process from the host buffer to a local write buffer associated with the optical storage device. The data in the host buffer are available to the write buffer such that the write buffer is not underrun while the data storage medium is completely written without interruption.
A sixth embodiment of the invention is an electronic device that includes a recordable optical storage device and a host device with a main memory. A device driver is interfaced with the optical storage device, and a direct memory access controller is interfaced with the optical storage device. The device driver is programmed to execute steps to write the optical storage device, including allocating a portion of the main memory as a host buffer, and transferring data FIFO, using the direct memory access controller, between the host buffer and a write buffer in the optical device. Data in the host buffer is available to the write buffer such that the write buffer is not underrun while the data storage medium is completely written without interruption.
Among the advantages of the invention are one or more of the following. The write buffer on the recordable optical device requires less storage capacity to avoid buffer underrun. The rate specific data transfer steps minimize the effect of software latency on the recording process for the optical device, and require only a modest write buffer on the recordable optical device to absorb hardware latencies. The cost of an optical storage device is reduced without adding significant new infrastructure on the host or requiring extensive modification to existing host hardware. Existing legacy host DMA engines can be used to deliver the capabilities necessary to reduce recordable optical device buffering requirements.